When someone says that they have back pain and problems urinating I always think of a kidney infection. I am not a medical professional, but I do feel like if you are not getting an answer that you can live with, or if the answers your are getting don't seem to fit your symptoms, get another opinion. Wendy is right about the water too. Also, I suggest cranberry, or pomegrante juice. I think they have to do a blood test for kidney function to get the results, a urinalisis will not show a kidney infection, just that there is an infection.
In another post, I was ranting about how men don't go often enough to get things checked out. I am glad to hear that you are 19, and on top of this. Don't except an answer unless it makes sense to you. If you are in pain, complain until you get the answers you need. Men spend more time shopping for electronics, cars, and toys, then taking care of their health. Maybe your generation will change that sterotype.....
Good Luck,
Karen